DESCRIPTION (prepared by applicant): The specific aim of this application is to determine if glucose control can be safely improved in children with type 1 diabetes as a result of using continuous glucose monitoring (CGM). In an initial feasibility trial, accuracy of the two CGM devices will be compared to venous glucose levels in a Pediatric GCRC. Children with and without diabetes will spend 24 hours in the GCRC. This will also help to sort out children with diabetes (1 in 30) who have excessive skin reactions to the GlucoWatch, or who cannot tolerate subcutaneous CGM sensors. The children with diabetes will then be randomized to a feasibility three-month trial of either using the GlucoWatch Biographer or the MiniMed CGMS or serving as a control. Children will be selected for the feasibility and the two-year study who are either using intensive diabetes management or who are committed to moving toward intensive diabetes management. They must be willing to do at least four self-blood glucose monitoring (SBGM) tests each day. They will be randomized to two years of treatment, including six months of using four GlucoWatch Biographers per week (two day/two night), six months of using the MiniMed CGMS, and a six month control period. Primary end points will be change in HbA1c levels and the incidence of hypoglycemia. HbA1c levels will be determined initially and every three months, or at one and three months in the feasibility trial, with a goal of achieving HbA1c values less than seven percent. The incidence of all hypoglycemic events and of severe hypoglycemia will be compared for the three treatment groups in the three-month feasibility and the two-year longer trial. In addition, each person will serve as their own control in the longer trial as they are randomized to each of the three study groups. Secondary end points will be episodes of ketoacidosis, change in BMI, numbers of sensors used, insulin dose, use of an insulin pump, use of carbohydrate counting, number of SBGM tests done per day and changes in Fear of Hypoglycemia and Quality of Life Questionnaires. Quality of Life and Fear of Hypoglycemia Questionnaires will be used to evaluate psychological factors in both the factors in both the feasibility and the two-year trials.